Were you going to show us the screen shots?

I thought I did. I’ll try posting them again

Weird, it didn't show up for me yesterday, but does today.

I see Calc Load of 94.5% at 67MPH. That seems weird.

Why is that weird?

Because a 2011 Sierra 1500 5.3 4WD shouldn't be at 94.5% calculated load at 67MPH unless it is going up a steep hill or towing a heavy trailer or something.

I was going up a hill when the check engine light came on.

I'm going to circle back to oxygen sensors. I wonder if you're getting a flaky reading from one or more of them.

I looked at the load, TPS and RPM and it seems to be off. We have three different FF'* with the same time stamp. They all appear to have a substantially higher calculated load than should be.
Are we sure we don't have a vacuum leak?

The only place I suspect a leak is at the exhaust manifold On the driver side. I’m going to do a smoke test and see if that leads to anything.